One form of planographic printing is lithographic printing which relies on the immiscibility of oil and water, wherein the oily material or ink is preferentially retained by the image area of a lithographic printing plate. When a suitably prepared surface is moistened with water and an ink is then applied, the background or non-image area retains the water and repels the ink while the image area accepts the ink and repels the water.
The ink on the image area is then transferred to a surface of a material upon which the image is to be reproduced, such as paper, cloth and the like. Commonly the ink is transferred to an intermediate material called the blanket which in turn transfers the ink to the surface of the material upon which the image is to be reproduced. Because planographic printing is an ‘impact method’ of printing, the elements are subjected to considerable pressure and abrasion while used to print multiple images.
The production of printing elements for use in lithographic printing requires the formation of a hydrophilic layer on a substrate.